The present invention is directed to a tool bit chuck for securing a tool bit having an insertion end with at least one axially extending slot closed at the opposite ends transversely of the axial direction and at least one axially extending slot which is opened at the end of the tool bit inserted into the chuck. The tool bit chuck includes a guide sleeve with first apertures for locking members displaceable by an axially displaceable or rotatably displaceably adjusting sleeve for directing the locking members radially inwardly into the closed ended slots in the tool bit. In addition, the adjusting sleeve can displace entrainment strips radially inwardly through second apertures in the guide tube into the open ended slots in the tool bit.
Tool chucks of the above type are used mainly in hammer drills in which a tool bit can be operated for one of or the combination of rotational and percussive movement. In such a tool chuck, the tool bit is supported in the guide tube so that it rotates with the tube, however, it can effect limited axial movement relative to the guide tube.
In actual practice, tool bits have been widely used which are equipped with at least one axially extending slot closed at its opposite ends and at least one separate axially extending slot open at the end of the tool bit inserted into the chuck. In a tool chuck for such tool bits the open end axially extending slots serve to receive entrainment strips mounted in the guide tube for transmitting rotational movement from the guide tube to the tool bit. The locking members in the closed-ended slots serve only to secure the tool bit in the tool chuck. Such tool bits and tool chucks adapted to receive them have proved to be particularly effective where higher torques are developed, since it is possible to separate the functions of rotational entrainment and axial retention. This separation of functions is not available in the common type of tool bit with only at least one closed-ended axially extending slot. This known type of tool bit is unsuitable for higher torques. To eliminate the shortcomings with such known tool bits, tool bit chucks with entrainment strips have found increasing acceptance in hammer drills. There is the disadvantage, however, that the generally used tool bits with only at least one closed-ended axially extending slot can not be utilized in such chucks.